1. Field of the Invention
The present invention relates to streaming data and more specifically relates to a system and method of streaming 3-D wireframe animations.
2. Introduction
The Internet has rapidly evolved during the past few years from a low-bandwidth, text-only collaboration medium, to a rich, interactive, real-time, audio-visual virtual world. It involves many users, environments and applications, where 3-D animations constitute a driving force. Animated 3-D models enable intuitive and realistic interaction with displayed objects and allow for effects that cannot be achieved with conventional audio-visual animations. Consequently, the current challenge is to integrate animated 3-D geometry as a new data stream in the existing evolving infrastructure of the Internet, in a way that both enhances the existing networked environment and respects its limited resources. Although static 3-D mesh geometry compression has been actively researched in the past decade, very little research has been conducted in compressing dynamic 3-D geometry, which is an extension of static 3-D meshes to the temporal domain.
The most prevalent representations for 3-D static models are polygonal or triangle meshes. These representations allow for approximate models of arbitrary shape and topology within some desired precision or quality. Efficient algorithms and data structures exist to generate, modify, compress, transmit and store such static meshes. Future, non-static, stream types that introduce the time dimension, would require scalable solutions to survive with respect to the network's limited resources (bandwidth) and characteristics (channel errors).
The problem of 3-D wireframe animation streaming addressed herein can be stated as follows: Assume (i) a time-dependent 3-D mesh has been scalably compressed in a sequence of wireframe animation frames, (ii) the available transmission rate R is known (or determined with respect to the corresponding TCP-friendly rate), (iii) the channel error characteristics are known, and (iv) a fraction C of the available transmission rate (C<R) can be reserved for channel coding. Then, the issue is to identify the optimal number of bits to be allocated to each level of importance (layer) in the animation scene that maximizes the perceived quality of the time-dependent mesh at the receiver.
Most animation coding approaches use objective metrics to achieve a hierarchical coding of static 3-D meshes. What is needed is an animation approach that utilizes a subjective quantity, such as visual smoothness, to provide an improved appearance of animation. Described herein is a 3-D wireframe animation codec and its bitstream content, along with the associated forward error correction (FEC) codes. The visual distortion metric as well as the unequal error protection (UEP) method and receiver-based concealment method are further explained.